1. Field of the Invention
The present invention relates to an automatic anti-oxidation replenisher control system for use in processors of photosensitive material.
2. Description of the Prior Art
Automatic photographic film and paper processors transport sheets or webs of photographic film or paper through a sequence of processor tanks in which the photosensitive material is developed, fixed, and washed, and then transport the material through a dryer. It is well known that photographic processors require replenishment of the processing fluids to compensate for changes in the chemical activity of the fluids.
First, it has been recognized that replenishment is necessary to replace constituents used as photosensitive film or paper is developed in the processor. This replenishment is "use related" or "exhaustion" chemical replenishment. Both developer and fix solutions require exhaustion replenishment.
Second, chemical activity of the developer solution due to aerial oxidation occurs with the passage of time regardless of whether film or paper is being processed. Replenishment systems provide additional replenishment of an "anti-oxidation" (A-O) replenishment solution which counteracts this deterioration.
Replenishment systems were originally manually operated. The operator would visually inspect the processed film or paper and manually operate a replenishment system as he deemed necessary. The accuracy of the manual replenishment systems was obviously dependent upon the skill and experience of the operator.
Various automatic replenishment systems have been developed for providing use-related replenishment. Examples of these automatic replenishment systems include U.S. Pat. Nos. 3,472,143 by Hixon et al; 3,529,529 by Schumacher; 3,554,109 by Street et al; 3,559,555 by Street; 3,561,344 by Frutiger et al; 3,696,728 by Hope; 3,752,052 by Hope et al; 3,787,689 by Fidelman; 3,927,417 by Kinoshita et al; 3,990,088 by Takita; 4,057,818 by Gaskell et al; 4,104,670 by Charnley et al; 4,119,952 by Takahashi et al; 4,128,325 by Melander et al; and 4,134,663 by Laar et al.
Examples of prior art replenisher controls for providing both exhaustion and anti-oxidation replenishment are shown in U.S. Pat. Nos. Re. 30,123 by Crowell et al and 4,174,169 by Melander et al. In particular, these patents show systems which are usable to control anti-oxidation replenishment when a type of anti-oxidation replenishment known as "blender chemistry" is used. Blender chemistry is based upon a "minimum daily requirement" of anti-oxidation replenishment. This minimum daily requirement is dependent upon the amount of aerial oxidation which occurs in the developer tank, which in turn is dependent upon the open surface area of the tank, the operating temperature of the developer solution, and a number of other factors. With blender chemistry, some anti-oxidation replenishment is provided each time that exhaustion replenishment occurs. The more exhaustion replenishment provided, the less separate anti-oxidation replenishment is required.
Crowell discloses a variable quantity, fixed time anti-oxidation replenishment control in which a variable amount of anti-oxidation replenishment needed due to aging is determined at fixed time intervals based upon the replenishment provided by use or exhaustion replenishment during the time interval. At fixed time intervals, a needed amount of anti-oxidation replenishment is added, which varies from zero up to a predetermined maximum amount. The more exhaustion replenishment provided during the time interval, the less anti-oxidation replenishment is required. The apparatus in Crowell does not consider, however, the situation where more anti-oxidation replenishment than is needed is provided by the exhaustion replenishment. Thus overage can lead to an accumulated error in the Crowell system. Overreplenishment of anti-oxidation fluid will produce incorrect processing results, just as will underreplenishment. There is no recognition in Crowell that this error accumulation can occur, or of any way to resolve it. In addition, the system of Crowell et al is limited by its use of analog electronics and electromechanical cams, which make the system difficult to calibrate and limit the number of control options available to the user.
Melander et al discloses a fixed quantity, variable time anti-oxidation system based on a counter which is set to a predetermined value and then counted down over time to measure oxidation of processor fluid. When the counter reaches zero, a fixed amount of anti-oxidation replenisher is added. The counter is counted up to reflect anti-oxidation replenishment provided as a result of exhaustion replenishment.